Radio receiving system



Dec.. 6, 1927. LGSLSS L.. C. YOUNG RADIO RECEIVING SYSTEM Dec. 5, 1927. 1,651,658 L. c. YOUNG RADIO RECEIVING SYSTEM Filed oct. 24, 1925 2 sheets-sneer 2 ETE- 11.

Patented Dec. 6, 1927.p

UNITED STATES mio c. YOUNG, or WASHINGTON, marmer or continuara.

RADIO RECEIVING SYSTEM.

Application led October 24, 1925. Serial No. 64,658.

My invention relates 'broadly to radio receiving systems, and more particularly to a system for electrostatically shielding the receiving circuits.

One of the objects of my invention is to provide a practical construction of electrostatic shield for the circuits of an electron tube radio receiving system where undesired capacity coupling between parts ot a sensitive multi-tube amplifier may be eliminated.

Another object of my invention 1s to pro- -vide a construction of electrostatic shield ici' the circuits of a multistage radio frequency ampliication system where eddy current losses are reduced to a minimum, permitting free electromagnetic transfer of energy from one electron tube circuit to a succeeding electron tube circuit lwhile preventing capacity coupling between the electron tube circuits of the amplier.

Another object of my invention is to provide a construction of electrostatic shield for the circuits of a radio frequency amplifier system which may be practically manufactured on a quantity production bases at small cost for effectively preventing capacity coupling between the several parts of an electron tube amplifier system without interfering with the electromagnetic coupling between the several circuits of the amplifier.

A further object of my invention isl to provide a construction of electrostatic shield positioned between the windings of the coupling transformers which link the input and output circuits of an electron tube amplifier in which the several parts of the electrostatic shield are open-circuited for preventing the flow of eddy currents therein with the parts of the shield spaced apart in the manner of a screen for 'freely permitting the transfer of electromagnetic energy between windings disposed on opposite sides of the shield while preventing the electrostatic transfer of eneigy between the windings.

A still further object of my invention is to provide a method of manufacturing electrostatic shields for electrostatically isolating the primary and secondary windings of the coupling transformers in a radiofrequency amplifying system where the shield may be formed by winding insulated wire on a frame, providing a conductive bond for one end 0f the wires and cutting the wires at the opposite end away from the'frame for forniing a Hat surface composed of conductors insulated from each other and bonded together at one end thereof comprising the electrostatic shield.

My invention will be more clearly understood by reference to the following specification and the accompanying drawings, in which:

Figure l is a theoretical view illustrating the electrical capacity existent between the primary and secondary windings of a cou-- pling transformer in an electron tube amplifying system; Fig. 2 illustrates a shield interposed between the transformer windings and connected to ground; Fig. 3 illustrates the principle of my invention where an electrostatic shield is interposed between the primary and secondary windings of a coupling transformer, the shield being formed of parallel conductors electrically free at one end and bonded at the other end and connected to ground; lllig. 4r is a perspective view illustrating a metallic shield in which the circuits of a sensitive electron tube amplier of a radio receiver may be disposed,

and showing the application of my invention to a pair of coupling coils in the apparatus; Fig. 5 illustrates one method of manufacturing the electrostatic shield construction of my invention; Fig. 6 is a partial cross-sectional view taken on line 6 6 of Fig. 5 and showing the method l may employ in manufacturing several electrostatic shields simul`v taneously; Fig. 7 is a fragmentary cross-sec tional view taken on line 7-7 of Fig. 5 and showing the relationship of the conductors forming the electrostatic shield after the conductors have been coated with a material for securing the wires rigidly vin position; Fig. 8 is a theoretical view illustrating the principle of my invention; Fig. 9 shows an application of my invention to the tuning system of a radio receiver utilizing a multistage amplifier; Fig. l0 illustrates an application of my invention to a receiving system utilizing an intermediate tuning circuit for selective reception; and Fig. l1 shows the method of arranging several electrostatic shields constructed in accordance with my invention between the coupling transformers which interlink a plurality of electron tubes in a radio frequency amplifying system.

Heretofore in the art attempts have been made to electrostatically shield parts of sensitive electron tube amplifier systems, but in so doinglarge eddy current losses have been introduced, and in suppressing the electrostatic shield the magnetic coupling between the windings of the coupling transformers has been considerably reduced. By my invention I provide an electrostatic shield composed of i a plurality of parallel extending conductors insulated one from another by the insulated covering on the individual conductors and electrically bonded at one end for connection to ground and being electrically free at the opposite ends. By providing an electrostatic shield without closed electrical circuit I substantially eliminate eddy current losses, and by reason of the separation of the 'conductors electromagnetic lines may readdy thread through the electrostatic screen while the passage of an electrostatic field is prevented, thereby eliminating capacity coupling directly with respect to, the grid circuit of succeeding electron tubes of a series. I provide means for manufacturing electrostatic shields inexpensively on a quantity production basis by winding an insulated conductor around a Hat frame, scraping the insulation from the conductors at one edge of the frame and bonding -the conductors electrically at that end. At the opposite end the conductors may be cut, leaving downwardly depending parallel conductors bonded together at the opposite end in the general contour of a comb or fork having a great many projecting teeth. Prior to the cutting of the conductors and the remo-val thereof from the frame, a coating of celluloid composition or. suitable binding material is applied to the insulated conductors tending to draw or shrink the conductors together, forming a rigid flat surface. An electrostatic shield may be constructed in this manner on bot-h sides of the frame, and both shields severed from the frame for installation in a radio receiving apparatus.

My invention'will be understood in more detail by reference to the drawings where,

in Fig. 1, I show a primary winding 1 electromagnetically coupledv with a secondary winding 2 of a transformer system The magnetic lines which link the primary and secondary windings are represented at 4. The inherent electrostatic capacity existent between windings 1 and 2 has been represented by a'condenser having plates 5 and 6.

In Fig. 2 I have shown one'method by which the inherent electrostatic field between the windings 1 and 2 of the transformer 3 can be suppressd. A plate 7 may be interposed between the windings and grounded, as indicated at 8. There is however a considerable eddy/current loss introduced by the use of this shield and the magnetic coupling of the windings is practically prevented, although the electrostatic field is suppressed.

In Fig. 3 I have illustrated the arrangement of the electrostatic shield which I pro vide for avoiding the disadvantages heretofore encountered. Conductors 9 extend from a common bus connection 10 which extendsl laterally across one end of the conductors and is grounded, as represented at 8. There is no continuous electrical circuit through the conductors 9 and for this reason eddy current losses are substantially negligible. The electromagnetic field threads through the screen between the conductors 9 while the electrostatic iield is suppressed.. The interposition or" a shield of this kind between windings 1 and 2 eliminates capacity coupling directly on the grid o' succeeding tubes of a series.

In Fig. 10 I have illustrated the metallic lining which is generally provided within the cabinet of a sensitive electron tube radio receiver. I provide a metallic lining 11 which is formed into sections 12, 13 and 14 to house ,the different parts of the radio receiver. For example, the tuning apparatus for the receiver may be disposed in compartment 14. The electron tube amplification system for the receiving apparatus may be disposed in compartment 12, while compartment 13 may house the batteries for operating the power circuits of the apparatus. A partition 15 divides the cabinet laterally and is provided with an aperture therein which is-fclosed by means of the shield described in Fig. 3 where the bus connection 10 extends along the partition at the upper extremity of the aperture with downwardly depending conductors 9 connected therewith. A primary winding 16 is illustrated on one side of the screen conductors 9 coupling with a secondary winding 17 on the opposite side of the screen conductors 9. Primary winding 16 may be angularly adjusted with respect to secondary winding 17 by means of a control 18. The metallic lining is grounded -at 8 which grounds the shield conductors 9 through the metallic circuit formed by the partition 15. In Fig. 5 I have illustrated one of the methods of manufacturingthe electrostatic shield where a flat frame 1 9 is provided and the conductors 9 arranged thereon by winding insulated wire, such as cotton covered wire, with the turns directly adjacent each other so that the. insulation 9c and 9", as shown more clearly in Fig. 7 serves to positively space each turn of the conductor 9 from each other. The upper edge of the conductors 9 is scraped free of insulation and bus bar 10 soldered along the conductors, thereby connecting all of the conductors to get-her at the upper ends. Similarly, a strip or bus bar connection 23 is soldered to the ends of conductors 9 on the opposite side of frame 19, The conductors are then coated pending conductors.

with a celluloid composition or material resembling that which is spread upon fabric used. in the manufacture `of aircraft which shrinks the insulation and draws the conductors together as it dries, leaving a fiat rigid plate formed of thedownwardly de- The conductors may then bereut alon lines AA at 20 and 21., as represented in Fig. 6, and the free ends bent over bonds 10 and 23 securing the conductors ri idly together at one end/while being electrlcally free at the other end.

In Fig. 8 I have illustrated the arrangement of the coupling coils 16 and 17 'on opposite sides of the screen 9 where the magnetic lines 4 and 41 readily pass through the shield conductors 9 while the electrostatic effects are neutralized. The primary winding 16 may be moved into the dotted line position '16 through desired angular displaceme-nts along axis 18.

In Fig. 9 I have shown a radio receiver embodying the principles of my invention where a radio frequency energy collecting circuit in the form of a loop 24 connects through variable condenser 25 with the primary Winding 1 disposed on one side of the electrostatic shield forme-d by conductors 9. On the other side of the electrostatic shield the secondary coil 2 is magnetically coupled with the primary winding 1. The coil 2 is tuned 'by means of variable conl denser 26 and connects with the input ycircuit of a radio frequency amplifier system consisting of tubes 27, 28 and 29 connected `with a'detector tube 30, the output of which connects to an audio frequency amplifier comprising tubes 31, 32 and 33. I have illustrated tubes 32 and 33 as having their electrodes parallel connected for developing a large amplitude of ener for actuating the reproducer which may e connected to jack 36 in the outputcircuit. The plate supply for the severa'l tubes is taken from battery 35 while the cathodes are heated from battery 34. A suitable tap may be provided on battery 35 for securing the desired potential for operation of detector" tube 30. The required bias potential for the grids ofthe radio frequency amplifier tubes may be obtained from a tap which is movable over a potentiometer connected in shunt with battery 34.

In Fig. 10 I have illustrated a. receiver system in which a pair of electrostatic Yshields 9 and 41 are provided in the apertures formed in partitions 15 and 40, electrostatically shielding inductances 1 and 2 and inductances 38 and 39. Inductance 38 i'sconnected to variable condenser 37 and the inductance 2, thus forming an intermediate tuned circuit which is magnetically coupled to the inductance 1 in the signal receiving circuit and inductance 39 1n the amplier circuit, but electrostatlcally isolated therefrom. Inductance 39'is tuned by means of variable condenser 42 and the received energyimpressed upon electron tube 43.

vIn Eig. 11 I have illustrated a tuned radio frequ'ncy ampllfier where the electrostatic coupllng between parts of the several electron tube circuits 1s prevented by means of electrostatic shields constructed in accordance with my invention. The first stage 27 of radio frequency amplification is electrostatically shielded' from the radio frequency magnetically coupled with inductance 50 connected in the tuned circuit 51 with the succeeding stage of amplification but electrostatically isolated therefrom by` means of screen 48 in the conductive partition Wall 47.

In the construction'of'the radio receiving apparatus I prevent the passage of radio .1

frequency energy along the leads which pass through the partition walls 40 and 47 by shunting away the radio frequency energy through condensers, as has been illustrated. One sideof the variable tuning condensers in each ofthe stages is defined at ground potential by a connection taken through the shield 11, as shown.

My invention has been found to be very practical in its construction and efficient in lill) operation for preventing undesired electrostatic transfer of energy while permitting the electromagnetic coupling where it is intended. y

While I have illustrated my invention in one of its preferred embodiments and described one method byrwhich the electrostatic screen may be manufactured, it will be .understood that modifications may be made in the arrangement of the electrostatic shield and that other methods may be ein-- ployed in its manufacture without departing from the spirit, of my invention, and no limitations are intended other than are imposed by the scope of the appended claims.

What I claim and desire to secure by Leters Patent of the United States is as folows:

1. In an electron tube amplification system the combination of a plurality of electron tubes each having grid, filament and plate electrodes, input and output circuits interconnecting said electrodes, means coupling the output circuit of one of said elec* tron tubes with the input circuit of a sucllt) cecding electron tube, and means interposed between said coupling means comprising a plurality of longitudinally extending conductors disposed in the same plane and electrically l'rce at one end and grounded for electrostatically shieldingl one of said electron tube circuits from another.

2. In an electron tube amplification system the combination of a plurality of electron tubes each having grid, filament and plate electrodes, input 'and output circuits interconnecting said electrodes, transformers having primary and secondary windings tor coupling the output circuit of one of said electron tubes with the input circuit of a succeeding electron tube and means interposed between said windings comprising a plurality of conductors disposed in the same plane and electrically open-circuited at one end and grounded at the other end for electrostatically shielding one of said windings from the other.

3. In an electron tube amplification system, the combination ot a plurality ol electron tubes, each having grid, filament and plate electrodes, input and output circuits interconnecting said electrodes, transformers having primary and secondary Windings for coupling the output circuit of one of said electron tubes with the input circuit of a succeeding electron tube, and means interposed between said win-dings comprising a plurality ot parallelly extending conductors disposed in the same plane and electrically insulated throughout their length one from another and electrically open-circuited at one end and bonded together at the opposite' end and connected to ground for electrostatieally shielding said primary and secondary windings. y

4. In an electron tube amplification system, the combination of a plurality of electron tubes, each having grid, filament and plate electrodes,input and output circuits interconnecting said electrodes, transformers having primary and secondary windings forcoupling the output circuit of one of said electron tubes with the input circuit ot' a succeeding electron tube. and means inter-- posed between said windings comprising a flat electrical conductive member having a plurality ot' conductive teeth exten-ding between said primary and secondary windings for electrostatically shielding said windings from each other while permitting the 'free electromagnetic coupling of said windings.

5. In a system for coupling a plurality of electrical circuits` the combination of induetively related coils and a screen interposed between said coils consisting of parallelly extending conductors electrically bonded to ground at one end and open-circuited at the other end for the free passage of magnetic lines from one coil to another, while electrostatic transfer' of energy therebetween is prevented. l

G. In a system for coupling electrical cir cuits, the combination of a plurality of inductively related coils and an electrostatic shield extending between said coils consisting of a plurality of electrical conductors dispose-d in the same plane and each insulated one from another throughout thir length and bonded together and placed at ground potential' at one end and open-circuited at the opposite end :tor permitting the electromagnetic coupling of said coils and preventing electrostatic coupling thereof.

7. In a system tor coupling electrical circuits the combination of a plurality of in ductively related windings, an electrostatic shield extending between said windings comprising a plurality of longitudinally extending electrical conductors disposed in the same plane, each coated with a laye'r of insulation and separated from each other by the insulated covering therearound, adjacent ends of said conductors being electrically bonded together and placed at ground potential, and the opposite ends of said conductors being electrically free for permitting the electromagnetic coupling of said windings while preventingy the electrostatic transfer of energy from `one winding to another.

8. In a system for coupling a plurality of electrical circuits, the combination of a plurality of ,inductively related windings and an electrostatic shield interposed between said windings comprising a flat sheet formed by parallelly extending conductors each insulated one from the other for allowing magnetic lines from one ot' said windings to thread through said fiat sheet for coupling with another ofsaid windings, one end of each of said conductors being connected to ground while the opposite ends are opencircuite-d, whereby electrostatic transfer ot energy from one of said windings to another is prevented.

9. In a system for coupling electrical circuits comprising in combination a pair ot windings iuduelively related along a common axis, an electrostatic shield comprising a flat sheet extending in a plane substantially perpendicular to the axis of said windings, said lat sheet being composed of a plurality of parallelly extending conductors insulated onel from another, whereby magnetic lines of force from one of said windings may thread through said flat sheet and couple with said other winding, one end of each of said conductors being connected to ground for preventing the electrostatic transfer of energy lfrom one winding to another.

].0' In a System :for coupling electrical cir,

cuits the combination of a plurality of inductively related coils, and a flat rigid sheet ot'material composed of a plurality of: closely adjacent metallic conductors each covered with insulation material united by a n0nconductive coating for securing said conductors in a plane perpendicular to the axis "of said coils, said conductors being grounded at one end and open-circuited at the opposite end for eliminating eddy currents in said shield, preventing the transfer of electrostatic energy from one of said coils to the other While permitting the free electromagnetic coupling of said coils.

ln testimony whereof I aix my signature.

LEO C. YOUNG. 

